Antenna switching circuitry is used to connect one or more radio frequency (RF) antennas to any number of signal paths in RF front-end circuitry in order to transmit and/or receive RF signals from an RF communications device. Due to considerations such as RF signal power, adjacent RF communications bands, and spectral masking requirements, one or more of the signal paths in the RF front end circuitry may require a particularly low distortion path to or from the antenna. For example, band 13 is adjacent to a reserved public safety band, and therefore is subject to strict spectral masking requirements in order to avoid producing interference therein. As a further example, band 17 is also adjacent to a reserved band, and therefore must also meet strict spectral masking requirements. Generally, these spectral masking requirements can be met by reducing harmonic distortion in the antenna switching circuitry. Accordingly, many designers have turned to antenna switching circuitry utilizing large (e.g., ≥3.5 mm) switching elements. Large switching elements generally have lower on-state impedances than their smaller counterparts, which may reduce harmonics generated from a signal passing through a particular switching element. While generally effective for reducing interference, the relatively low on-state impedance associated with large switching elements comes at the expense of increased parasitic capacitance. With an increase in the parasitic capacitance of the large switching elements comes a commensurate increase in insertion loss, and further may mandate the use of additional matching circuitry along with the antenna switching circuitry which further increases insertion loss and design size.
While the increased parasitic capacitance may be a necessary trade-off for one or more signal paths, over-designing antenna switching circuitry using large switching elements for every signal path in the RF front-end circuitry generally degrades the performance of the antenna switching circuitry. Accordingly, some designers have used custom antenna switching circuitry which utilizes a combination of large switching elements and smaller switching elements as the requirements of the RF signal paths coupled to the antenna switching circuitry mandate. While generally effective at decreasing interference while striking an adequate balance with insertion loss, such solutions must be custom designed for the RF front-end circuitry with which they are used, resulting in significant increases in design and manufacturing expenses.
In light of the above, there is a need for antenna switching circuitry with low distortion characteristics and low insertion loss that is adaptable to different RF front-end circuitry and RF signal path assignments to the antenna switching circuitry.